tchannel: map all yarpcerrors codes

[azylman]

Today, if someone uses yarpcerrors with the tchannel transport (e.g. in a middleware) many error types get mapped to tchannel's unexpected-error error code. Systems assume that unexpected-error indicates a server error, so this causes inaccuracies in metrics, logging, SLA reporting, etc.

This PR maps all yarpcerrors codes to a corresponding tchannel error code. Most of the missing ones were client errors, so in most cases the closest tchannel error code was ErrCodeBadRequest.

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[jkanywhere]

Looks good to me. I agree YARPC should support all the error codes for all the protocols.

YARPC codes are described in yarpcerrors/codes.go.